Compounded hydrocarbon fuels



United COMPOUNDED HYDRGCARBGN FUELS No Drawing. Application March 22,1955 Serial No. 496,077

' Claims. (Cl. 44-62) This invention relates to an improvement inhydrocarbon fuels, and particularly hydrocarbon distillate fuels, to theextentthat they are stabilized against deposit formation under varyingconditions of static and dynamic flow incident to ultimate introductioninto a combustion zone.

The. deposit-forming tendencies of hydrocarbon fuels, and particularlythe petroleum distillate fuels, are largely dependent upon theircomposition and the conditions to which they are subjected prior toenergy-release through combustion in :a combustion zone.Compositionwise, the deposit-forming tendencies or instability of thefuel are usually associated with the presence of thermally and/orcatalytically cracked componentsin the fuel and" become. increasinglypronounced in the higher boiling 'range'fuels. However, in:addition tothe effect of the organic components of the fuel, certain conditionsofstorage, transportation and serviceprior to combustion also contributematerially to the deposit-forming tendencies of the. fuel. Theseconditions are generally conditions of: oxidation and result in theformation of solublev and insoluble oxidation products which form thebulk of the deposits laid dovm on the various metal and other surfaceswithin the fuel system. Additionally,:the presence of nonhydrocarboncontaminants in the fuel, and particularly metals such as copper andiron, accelerates-the oxidative reactionsand coincident depositformation.

The more general oxidative' deterioration. is obtained asa lowtemperature oxidation during storage in the presence of air, and theresulting deposit formation is substantially dependent upon thecomposition or stability of the fuel. Other types of oxidativeconditions which, in addition, promote deposit formation are encounteredin the conditions and fuel systems specificto'the various types ofhydrocarbon fuels. Thus,.in: the operation of internal combustion:engines,.whether compression-igni tion or spark-ignition, depositformation is encountered within the inductionsystem. and particularly atthe intake valves, injector nozzles, and injection plungers. At theareas of deposit formation, the hydrocarbon fuel is subjected tocomparatively high temperatures and comes in contact with combustion andexhaust gases'containing oxidation precursors, etc. Another illustrationof specific deposit formation of hydrocarbon fuels isin the opera tionof aircraft gas turbine engines wherein the fuel may be employed as a.coolant and in heat exchange with the circulating lubricating oil. Insuch situations, the fuel is subjected to skin temperatures of up to 500F. and results in the deposition of coke-like deposits on the heatexchanger surfaces.

Although certain of these deposit-forming tendencies of the hydrocarbondistillate fuels maybe eliminated or minimized by additional refineryprocessing designedto extract, alter, and/ or remove theoxidation-sensitive and/ or unstable components of the fuel, suchpractices great- 1y depreciate theyield of fuel and materially increasethe unit fuel costs. However, contrasting the disadvantages ofadditional process refining ofthe distillate fuels, it has ties Patent2,892,690 Patented June 30, 1959 now beendiscovered that hydrocarbonfuels-may be stabilized against objectionable deposit formation prior tocombustion by the incorporation of a unique class of. addition agents.

According to thepresent invention, it has been found that theincorporation in a hydrocarbon fuel, and pref: erably a petroleumhydrocarbon distillate fuel, of a minor amount of a specific class ofrelatively high molecular weight copolymer compositions will effect amaterial reduction in the formation of insoluble sludges, etc., which"may be precipitated or carried with the fuel to form'deposits'within thefuel system and thereby reduce the operating efficiency of thecombustion engine or burner; The class of copolymer compositions whichhave been determined to be unique in these improving character-- isticsmay be defined as arelatively high molecular weight copolymercomposition which may be obtained by thecopolymerization of (A)'at leastone compound containing. an ethylenic linkage and 8 to 30 aliphatic orcyclo-- aliphatic carbon atoms which is copolymerizablethroughthe'ethylenic'linkage, and (B) at least one il-unsaturatedmonocarboxylic acid, and preferably an a ti-unsaturated aliphaticmonocarboxylic acid containingfromfi to 81 carbon atoms, which copolymeris so constituted that the ratio of (A) to (B) is within the range of0.5 to 10, and' in which 0 to about of the carboxyl groups of; component(B) are present in the form of a polar-substituted derivative.

Within the foregoing definition of the hydrocarbon fuel improving.agent, the particular composition chosen foroptimumelfectiveness isdependent largely upon the particular. type of hydrocarbon'fuel, itscomposition, and the environmental conditions to which the fuel issubjected prior to-introduction into a'combustionzone. Thus, thespecific copolymer composition employed in a motor gasoline for maximumeffectiveness in reducing the intake manifold deposits in aspark-ignition, internal combustion engine will usually. differchemically within the foregoing classification from the copolymeradditives incorporated in a high boiling burner fuel containing highconcentrations of cracked gas oil stocks to eflfect the maximumreduction in clogging: and plugging of filters, screens, pumps, and thelike. In general, the greatest improvement in reduction ofdeposit-forming characteristics of a hydrocarbon distillate fuel by theincorporation of the subject copolymer addition agentis obtained withdistillate fuels composed predominantly of hydrocarbons boil ing aboveabout 300 F., and the effective concentration of the copolymer additivewill usually vary between 0.0005 to 1.0% by weight.

For specific illustration of the effectiveness of these addition agentsin reducing the deposit-forming tendencies of a hydrocarbon fuel,reference is made. to the higher boiling range fuels, such as theaircraft gas turbine engine fuels, commonly referred to as jet fuels;kerosene; gas oils, and particularly the thermal and catalyticallycracked gas oils; compression-ignition, internal combustion fuels, suchas diesel fuels; and the conventional burner or furnace oils.Particularly for these types of fuel applications, it is desirable toemploy an addition agent within the class of relatively high molecularweight copolymers, which may be produced through copolymerization of (A)at least one compound comprising analiphatic ester containing 8 to 30carbon atoms and a copolymerizable ethylenic linkage alpha or beta tothe carboxylgroup, and (B) at least one copolymerizable compoundcomprising an a ti-unsaturated aliphatic mono, carboxylic acidcontaining from 3 to 8 carbon atoms, .to produce'a copolymer compositionin which the compo, nents (A) and (B) are present in the ratio of (A) to(B) within the range of 0.5 to 7, and in which 5- tov 60%. of.thecarboxyl groups of the component (B) are present in the form of apolar-substituted derivative such as the oxygenand/ornitrogen-containing esters, amides, and/ or amine salt derivatives.

The copolymerizable component (A) is primarily employed to impart therequired degree of oil solubility to the copolymer composition, and,according to the aforementioned definitions, includes the following:olefin hydrocarbons and particularly alkenes such as polyisobutylene anddodecene-l, cycloalkenes such as cyclohexene and vinylcyclohexane, andstyrenes such as p-octylstyrene and p-t-butylstyrene; olefinic ethers,representative of which are the vinyl ethers such as vinyl n-butylether, vinyl Z-ethylhexyl ether, and vinyl p-octylphenyl ether, allylethers such as allyl cyclohexyl ether and allyl isobutyl ether, andmethallyl ethers, such as methallyl nhexyl ether and methallyl octadecylether; organic esters in which the copolymerizable ethylenic linkage iscontained in the ester radical, such as the vinyl, allyl, methallyl andcrotyl esters of long-chain aliphatic and cycloaliphatic monobasicacids, illustrative of which are vinyl oleate, vinyl palmitate, allyllaurate, allyl stearate, allyl ricinoleate, allyl naphthenate, methallylcaproate, methallyl palmitate, crotyl oleate, crotyl naphthenate,a-methylcrotyl palmitate; organic esters in which the copolymerizableethylenic linkage is contained in the acid portion of the molecule, suchas the esters of acrylic, methacrylic, crotonic, maleic, citraconicacids, etc., representative of which are dodecyl acrylate, dodecylmethacrylate, cyclohexyl methacrylate, decyl vinylacetate, octadecylisocrotonate, didodecyl maleate, di-2-ethylhexyl fumarate, didodecylcitraconate, etc.

The other copolymerizable component, identified for convenience ascomponent (B), is employed for the purpose of supplying the requisiteactive polar constituents in the copolymer composition. As previouslyindicated, the fundamental structure of component (B) consists of amonocarboxylic acid, and preferably an aliphatic monocarboxylic acid,with a copolymerizable olefinic linkage in the a,fl-position tothe'carboxyl group. More specifically, component (B) is preferablyselected from the 18- unsaturated aliphatic monocarboxylic acids whichcontain [from 3 to 8 carbon atoms in molecule. Particularly preferred ascomponent (B) are the acrylic and methacrylic acids with theirsubstituted derivatives falling within the scope of the general formula:

in which R; and R are either hydrogen or lower alkyl radicals containingfrom 1 to 3 carbon atoms.

While component (B) has here been defined in terms of a freemonocarboxylic acid, the final copolymer composition may present up to80% of the carboxyl groups of component (B) in the copolymer in the formof their polar-substituted derivatives. These derivatives may beintroduced initially into the copolymerization reaction by employing asthe monomer (B) appropriate mixtures of the monocarboxylic acidderivatives and the free monocarboxylic acid, or the copolymerizationmay be effected with the monocarboxylic acid monomer and the resultingcopolymer reacted with the desired polar-substituted alcohol or an aminein appropriate ratio to effect the desired degree of derivativeformation.

The desirability of modifying the basic copolymer structure through theuse or by the formation of the carboxylic acid derivatives is primarilydependent upon the environmental conditions to which the compoundedhydrocarbon fuel is subjected. In addition to the previous variables incomposition of the base fuel and projected service conditions, a furtherselection of optimum copolymer composition is predicated upon thepresence or absence of water in the fuel system, e.g., wet or dry fuelsystem. It has been found that, in general, the modified copolymers inwhich up to 80%, and preferably from about 5 to 60%, of the carboxylgroups of component (B) are presented in the form of their oxygenornitrogencontaining esters or aminated derivatives possess certainperformance advantages when employed as an improving agent forhydrocarbon fuels in a wet fuel system. Aside from the improved depositreduction noted in performance tests in a wet burner fuel system, othercollateral improvements, such as corrosion inhibition and improveddemulsibility, are attained with proper selection of the copolymerderivatives.

The derivatives contemplated within the scope of the invention are suchderivatives as may be produced by conventional esterification oramination reactions with the carboxyl groups of component (B). Byamination" reaction is meant the generalized reaction of ammonia and itssubstituted derivatives, e.g., primary, secondary, and tertiary amines,with a carboxyl group, including the various stages of dehydration,e.g., amine salt, amide, imide, etc., formation. Although thesederivatives may be initially presented as an integral function of themonomer (B) to the copolymerization reaction, it is preferred to conductthe copolymerization reaction with the free monocarboxylic acid as thecopolymerizable monomer (B) and subsequently modify the resultingcopolymer by the partial esterification or amination reactions tointroduce the particular derivative functions in the desired degree.This preferred mode of preparation facilitates the conduct of acopolymerization reaction, yields a more uniform copolymer backbone, andpermits more latitude in the degree of derivative formation.

Since one of the primary objectives in the modification of a givencopolymer backbone is to increase the polar ratio of the copolymercomposition, the partial esterification and amination reaction arepreferably conducted to form derivatives containing at least one activepolar group. To this end, the partial esterification may be conductedwith aliphatic, cycloaliphatic, or aromatic monoand polyhydric alcohols,and the partial amination reactions with ammonia or monoand polyamineswithin a wide range of structural deviation and molecular weight.

For the purpose of illustrating the preferred form of derivatives, thefollowing representative types of alcohols may be employed in theformation of the esters. For the introduction of multiple polar groups,the glycols, glycerols, pentaerythritols, sorbitans, and polyalkyleneglycols and their condensation products may be employed. In thepolyalkylene glycols, the polyethylene and polypropylene glycols, eitherper se or in combination with varying molecular weights up to about 800,may be used. Additionally, the ethylene oxide condensation products withfatty amines, fatty acids, and fatty acid amides may also be employed.When esterifying with the polyhydric alcohols, for example, glycols andpolyethylene glycols, it is preferred to avoid the presence of a freeterminal hydroxyl group which may result in cross linkage within thepolymer structure as evidenced by gel formation.- This has been avoidedin the case of the polyethylene glycols by capping the residual orterminal hydroxyl radical with alkyl or other radicals.

On the other hand, representative amines which may be employed to formthe aminated derivatives include the monoand polyfunctional amines asrepresented by the primary, secondary, and tertiary aliphatic, aromatic,or alicyclic amines, which preferably contain up to 18 carbon atoms, aswell as the polyamines and polyfunctional amines including the aminoacids, amino alcohols, amino phenols, polyalkylenepolyamines,glyoxalidines or imidazolines and substituted derivatives thereof.

It has been particularly noted in the preferred application of thesubject copolymer improving agents in the higher boiling range fuels,such as those boiling predominantly within the range of from 300 to 700F., and preferably such fuels as contain appreciable concentrations ofcatalytically cracked gas oil stocks, that a certain optimumrelationship between the total number of aliphatic carbon atoms to polargroups within the molecule appears to exist. Evidence has been obtainedthat fora .given concentration the copolymer compositions containing aratio of aliphatic carbon atoms to polar groups within the range of from7 to 70 appear to embrace the optimum composition for deposit reductionefiectiveness. In determining this apparent balance between the polarand nonpolar constituents, the aliphatic carbon atoms to be consideredare the following: CH CH and excluding aromatic ring carbon atoms or thecarbon atom of the carbonyl groups. As polar groups, the followingrepresentative radicals are included: --O, OH (either acid, alcohol orphenol), NH

Am, .1 1 and excluding the carboxyl group of the substitutedderivatives.

Although considerable variation in ratio of component (A) and component(B) may be indulged, it has been found that the optimum performancecharacteristics of these copolymer improving agents, which may berepresented as A B are obtained when the ratio of component (A) tocomponent (B) lies within the range of from s 0.5 to 10, and preferablyfrom 1 to 7, or where m equals 0.5 to m, and preferably 1 to 7n. Inorder to attain the optimum ratios of (A) to (B) in the final copolymercomposition, it may be necessary or desirable to employ :a mixture ofmonomers for either or both components (A) and (B). For example, it isrecognized that certain monomers falling within the scope of thedefinition of component (A), such as the allyl esters, allyl ethers,vinyl esters, vinyl ethers, and alkenes, are difficult to copolymerizewith a component (B) monomer to a greater than l/l ratio. However, inthe event a ratio, (A) to (B), greater than 1 is desired, this may beaccomplished by employing a mixture of monomers using as the additionalmonomer (A'), for example, the acrylate esters, methacrylate esters,and/ or diesters of maleic, fumaric, citraconic, etc., acids, to resultin a copolymer composition A A 'B where m-l-m' equals 0.5 to 10.

The copolymerization of the monomers of component (A) and component (B)may be conducted in accordance with the conventional bulk, solution oremulsion methods of polymerization, with or without the presence of apolymerization catalyst or initiator, and the choice of the particularmethod of preparation will depend largely upon practical considerationsand the particular types of monomers to be copolymerized. However, thereaction is preferably effected in the presence of an inert organicsolvent, such as benzene, toluene, xylene, or petroleum naphtha, tofacilitate control of the reaction and handling of the resultingcopolymer. Various conventional types of'free radical-liberatinginitiators or polymerization catalysts may be employed; as, for example,the organic peroxides such as benzoyl peroxide, acetyl peroxide, t-butylhydroperoxide, or di'benzoyl peroxide; or an azonitrile such as1,1'-azodicyclohexane-carbonitrile or a, x-azodiisobutyronitrile. Inaddition, other means for initiating the copolymerization reaction maybe employed, such as the use of ultraviolet or gamma radiation, as maybe obtained from irradiation with a cobalt 60 source. The organiccatalyst or initiator may be employed in amounts of 0.1 to 10% byweight, and preferably in the range of 0.25 to 2%, which amounts may beincorporated in increments as the reaction proceeds. The temperature ofcopolymerization will vary, depending upon the selected monomericreactants and solvent employed, and may vary from about 75 to 150 C. The.copolymers formed may have a wide range of apparent g molecular weight,and usually of the order of' at least several thousands.

The majority of the desired copolymer compositions to be employed asimproving agents are substantially miscible in hydrocarbon oils, and maybe compounded into additive concentrates of at least 10% by weight, andpreferably up to 70% by weight. In the preparation of additiveconcentrates, the concentration of copolymer in the hydrocarbon vehicle,such as toluene, mixed xylenes, kerosene, or other petroleum fractions,may be limited by the tendency toward gel formation, and in suchinstances it has been found desirable to incorporate a modifying agentor polar solvent, such as dimethyl formamide, tetrahydrofuran,Z-methyltetrahydrofuran, dioxane, cresylic acids, propylene carbonate,etc., which function as solubilizing agents and cosolvents in thecopolymer concentrate. These modifying agents or cosolvents aregenerally employed in concentrations rang ing from 1 to 25% of theconcentrate. In addition to the copolymer improving agent of thisinvention, other conventional fuel additives which are compatible withthe copolymer improving agent may be incorporated into the concentratefor the purpose of facilitating the handling and blending problemsinvolved in the production of the finished hydrocarbon fuel.

As an illustration of the preparation of representative copolymers ofthe invention, together with their derivatives, the following examplesare presented. It is to be understood, however, that these examples arepresented solely for illustration and are not to be construed aslimitations of the invention compositions.

EXAMPLE 1 In this preparation of a copolymer of dodecyl (lauryl)methacrylate and methacrylic acid, the starting material employed was ahomopolymer of lauryl methacrylate (Acryloid 710). A solution of 14grams of potassium hydroxide in 300 milliliters of Z-ethylhexanol wasprepared, and to this solution was added 800 milliliters of a 40%solution in mineral oil of the methacrylate homopolymer. The amountofpotassium hydroxide employed constitutes a slight excess over thattheoretically required to eifect the desired saponification of approximately 15% of the ester groups present in the polymer.

The resulting solution was heated to 320 F. and maintained at thistemperature with stirring for 10 hours. To this solution was then added50 milliliters of benzene along with a 50% excess of 6 N-hydrochloricacid, theoretically required to liberate the free carboxyl groups fromthe corresponding salt. 'The acidified solution was then refluxed forover 8 hours, after which it was cooled, diluted with ethyl ether andWater washed (along with a small amount of ethyl alcohol to break theemulsion) until neutral to litmus. The solution was then placed in asteam bath to remove the ether, and thereafter distilled in vacuo untila pot temperature of 350 F. at 3 millimeters mercury was reached inorder to remove the Z-ethylhexanol and the dodecyl alcohol present. Theresulting copolymer of dodecyl (lauryl) methacrylate and methacrylicacid contained the approximate ratio, A /B Variations in the ratio oflauryl methacrylate to methacrylic acid or, in other words, component(A) to component (B), were obtained in accordance with the foregoingprocedure by modifications in the degree of saponification andhydrolysis.

EXAMPLE 2 The copolymer of dodecyl methacrylate and methacrylic acid,A7/B1, prepared in accordance with Example. 1, was dissolved in 300milliliters of a mixed toluene-xylene solvent, along with 0.15% (basedon the weight of the polymer) of toluene sulfonic acid and an amount ofn-octylamine, theoretically required to amidize 50% of the free carboxylgroups in the copolymer. The resulting solution was then refluxed for 8hours 7 while distilling off as an azeotrope the water formed during theamidization reaction.

The modified copolymer composition was then precipitated by the additionof an excess of an acetonemethanol mixture, following which thecomposition was acetone washed and stripped in vacuo to removelowboiling constituents. The resulting oil-soluble copolymer compositionso obtained was found to contain approximately 50% of the carboxylgroups in the methacrylic acid, component (B), in the form of theirnoctylamide derivative.

Similar preparations were conducted, employing the same basic copolymerand reacted to form the amides and amine salts using various types ofamines, such as monoethanolamine, dihydroxyethyl ethylenediamine, etc.,in varying degrees of derivative formation and stages of dehydration.

EXAMPLE 3 Into a 1-liter condensation flask, equipped with agitatingmeans, heat control and automatic water separator, was charged 350 gramsof dodecyl methacrylate-methacrylic acid copolymer (A /B 178 grams of adodecyl ether of a polyoxyethylene glycol containing an average of 10ethylene oxide units, 1 gram of p-toluene sulfonic acid, and 100milliliters of refined kerosene. The reaction mixture was continuouslyagitated for about 36 hours while maintaining a temperature of 400 F.and automatically separating the water of reaction. To a mixture of 570grams of the resulting reaction product and 50 milliliters of benzeneundergoing Vigorous agitation was added 500 milliliters of methanol and2000 milliliters of acetone for the purpose of extracting the excessalcohol and precipitating the copolymer composition. This total mixturewas then stirred for 5 minutes and allowed to settle for 30 minutes. Themethanolacetone extract was decanted. The precipitation procedure wasrepeated five additional times. The precipitated copolymer compositionwas then dissolved in a 140 neutral lubricating oil from a Californiawaxy crude to yield a 45.25% concentrate. Electrometric titration(sodium methylate procedure) indicated that the carboxyl groups ofcomponent (B) were esterified to the extent of 25.8%.

Further preparations were repeated in accordance with the foregoingprocedure employing copolymer backbones of varying composition and ratioto esterify the carboxyl groups of component (B) with representativetypes of alcohols and in varying degrees of esterification.

EXAMPLE 4 This example illustrates the copolymerization of the monomericcomponents, dodecyl methacrylate and meth acrylic acid. Into a 1-litercondensation flask, equipped with agitation, heat control, etc., wascharged 300 grams of dodecyl methacrylate, 100 grams of toluene, 50grams of benzene, and 17.55 grams of glacial methacrylic acid. Thismixture was stirred and heated to 226-230 F. A catalyst solutioncontaining 6.43 grams of benzoyl peroxide dissolved in 100 grams oftoluene was slowly added. After all the catalyst was added, the totalreaction mixture was stirred at 220230 F. for 8 hours.

At the conclusion of the polymerization reaction, 100 grams of thereaction mixture was dissolved in 70 grams of benzene, and vigorouslyagitated. While stirring vigorously, 316 grams of acetone and 78 gramsof methanol were added to precipitate the dodecylmethacrylate-methacrylic acid copolymer. The precipitated copolymer wasrecovered and dissolved in a solvent-refined lubricating oil of an SAE30 grade to result in a 39.4% concentrate. Electrometric titrationindicated a ratio of dodecyl methacrylate to methacrylic acid of 5.5/1,or, in other words, 5.5 1-

To ascertain the merits of the subject improving agents, andparticularly their merits in regard to deposit reduction in unstable,high-boiling fuels, such as those as con tain appreciable concentrationsof cracked gas oils, a test procedure was established which has beendetermined to correlate with actual service conditions' This testinvolves the determination of the filter residue, or, in other words,the amount of insoluble solids of less than 100- mesh particle sizepresent in distillate fuels as received and the amount of insolublesolids which form in distillate fuels during aging at elevatedtemperature. The aging conditions are for 4 weeks at 140 F.

In determining the filter residue of fuels as received, the sample isscreenedthrough a 100-mesh sieve, and 500 milliliters are filteredthrough a tared Gooch crucible without adding diluent. The crucible iswashed with 500 milliliters of petroleum ether, dried in an oven at 190F., cooled in a constant-humidity vessel, and weighed. The filterresidue is calculated as parts per million.

In determining the filter residue of the fuel on aging, an additional500 milliliter sample of the fuel is filtered through filter paperintoan unstoppered l-quart bottle and stored at 140 F. for 4 weeks. At theend of this time, the sample is filtered through a tared Gooch crucible.The material adhering to the container is dissolved in 25 milliliters ofan /20 benzene-alcohol solution. The gums are precipitated by theaddition of 500 milliliters of petroleum ether, and the mixture is alsofiltered through the Gooch crucible. The crucible is then washed, dried,and weighed as previous.

The following filter residue test results were obtained with a number ofcopolymer improving agents of the invention, illustrating the effect ofvariations in mole ratio of the (A) and (B) components and modificationof the copolymer base by esterification and amination reaction with thecarboxyl groups of component (B) to form partial derivatives thereof. Inthese tests, the base fuel employed was a 50/50 blend of a raw Thermoforcatalytically cracked gas oil and a straight-run gas oil, blended tomeet the US. Commercial Standards specifications of a No. 2 fuel oil,and the copolymer improving agents were incorporated in each instance ina concentration of parts per million. The data are reported in terms ofthe percent improvement or percent reduction in filter residue over theuncompounded base fuel. For the sake of convenience, the base monomersof the copolymer compositions will be identified as A-laurylmethacrylate, B-methacrylic acid, and B'acrylic acid; and the subscriptfollowing the respective monomer indicates the approximate mole ratio ofthe monomer in the copolymer backbone. Following the designation of themodifying agent in the case where the copolymer backbone is esterifiedor aminated, the percentage figure in parentheses will indicate thedegree of esterification or amination.

Table I [Filter residue after storage 4 weeks at F.]

Reduction in Deposit Formation, Percent Additive Polyethylene glycol ofindicated molecular weight.

Further test data were obtained to illustrate the effectiveness of thecopolymer compositions in aircraft gas turbine engine fuels. Aspreviously indicated, certain recent models of aircraft gas turbineengines utilize the fuel as a coolant for the engine lubricating oil,and as a result have developed a problem of deposit formation on thefuel side of the heat exchanger. In this type of service, the fuel issubjected to temperatures in the range of 300 to 500 F., and to agreater or lesser extent gradually results in the fouling of the heatexchanger and fuel system lines with a coke-like deposit.

A test procedure was developed to correlate the effect of additionagents upon the stability of the engine fuel at elevated temperaturesmaintained over varying periods of time. In this test, open Erlenmeyerflasks containing 100 milliliters of test fuel are partially submergedin a heated oil bath. The temperature of the bath and time in the bathare varied to obtain the desired severity. After the samples are removedand cooled, they are filtered through No. 2 Watman paper disks. Thedisks are then rinsed with mixed hexanes, and the deposits ratedvisually. A rating scale is used which assigns a zero to a perectlyclean filter disk and 9 to a heavily deposited dis In the subject tests,the base fuel employed was a JP-3 fuel meeting military specificationsMTL-F-5624B. With the compounded fuels, the temperature was maintainedat 400 F. for 6 hours. As indicated in the following table, one testfuel was continued with hourly examinations to 10 hours. As previously,the base monomers of the copolymer compositions are identified asA-laury1 methacrylate, B-methacrylic acid. The following test resultswere obtained; and the subscripts following the respective monomersindicate the approxiigaate mole ratio of the monomer in the copolymerbackone.

Polyethylene glycol of indicated molecular weight.

Base fuel gave a rating of 9 at 350 F. for 2 hours.

Obviously, many modifications and variations of the invention ashereinbcfore set forth may be made without departing from the spirit andscope thereof, and therefore only such limitations should be imposed asare indicated in the appended claims.

We claim:

1. An improved fuel composition comprising a major portion of ahydrocarbon fuel and a minor portion, sufficient to reduce thedeposit-forming characteristics of said fuel, of a relatively highmolecular weight copolymer obtained by the copolymerization of (A)monomers selected from the group consisting of aliphatic esters ofmethacrylic acid and acrylic acid containing 8 to 30 carbon atoms and(B) monomers selected from the group consisting of methacrylic acid andacrylic acid in which the ratio of (A) to (B) is within the range of 0.5to

10, and in which from about to 60% of the carboxyl,

groups of (B) are present in the form of monoesters of polyalkyleneglycols selected from the group consisting of polyethylene glycol havinga molecular weight up to about 800 and monoalkyl ethers of saidpolyethylene glycol.

2. An improved hydrocarbon fuel composition comprising a major portionof a hydrocarbon fuel predominantly boiling above 300 F. and a minorportion, sufficient to reduce the deposit-forming characteristics ofsaid fuel, of a relatively high molecular weight copolymer producedthrough copolymerization of (A) dodecyl methacrylate, and (B)methacrylic acid to produce a copolymer composition in which thecomponents (A) and (B) are present in the ratio of (A) to (B) within therange of 0.5 to 10, and in which from about 5 to 60% of the carboxylgroups of component (B) are present in the form of monoestersofpolyethylene glycol having a molecular weight of about 400.

3. An improved hydrocarbon fuel composition comprising a major portionof a hydrocarbon fuel predominantly boiling above 300 F. and a minorportion, sufficient to reduce the deposit-forming characteristics ofsaid fuel, of a relatively high molecular weight copolymer producedthrough copolymerization of (A) dodecyl methacrylate, and (B)methacrylic acid to produce a copolymer composition in which thecomponents (A) and (B) are present in the ratio of (A) to (B) within therange of 0.5 to 10, and in which from about 5 to 60% of the carboxylgroups of component (B) are present in the form of monoesters of thedodecyl ether of polyethylene glycol having a molecular weight of about704.

4. An improved hydrocarbon fuel composition comprising a major portionof a hydrocarbon fuel predominantly boiling above 300 F. and a minorportion, sufficient to reduce the deposit-forming characteristics ofsaid fuel, of a relatively high molecular weight copolymer producedthrough copolymerization of (A) dodecyl methacrylate, and (B)methacrylic acid to producea copolymer composition in which thecomponents (A) and (B) are present in the ratio of (A) to (B) within therange of 0.5 to 10, and in which from about 5 to 60% of the carboxylgroups of component (B) are present in the form of a monoester ofoctadecyl ether of a polyethylene glycol having a molecular weight ofabout 400.

5. A concentrate adapted to be incorporated in by drocarbon fuels inconcentration elfective to reduce the deposit-forming characteristics ofsaid fuels consisting essentially of a hydrocarbon vehicle containingfrom 10 to by weight of a relatively high molecular weight copolymerobtained by copolymerization of (A) monomers selected from the groupconsisting of aliphatic esters of methacrylic acid and acrylic acidcontaining 8 to 30 carbon atoms, and (B) monomers selected from thegroup consisting of methacrylic acid and acrylic acid in which the ratioof (A) to (B) is within the range of 0.5 to 10, and in which from about5 to 60% of the carboxyl groups of (B) are present in the form ofmonoesters of polyalkylene glycols selected from the group consisting ofpolyethylene glycol having a molecular weight up to about 800, andmonoalkyl ethers of said polyethylene glycol.

References Cited in the file of this patent UNITED STATES PATENTS2,366,517 Gleason Jan. 2, 1945 2,370,943 Dietrich Mar. 2, 1945 2,469,737McNab et a1. May 10, 1949 2,584,968 Catlin Feb. 12, 1952 2,615,845Lippincott et a1. Oct. 28, 1952 2,666,044 Catlin Jan. 12, 1954 2,728,751Catlin et a1. Dec. 27, 1955 FOREIGN PATENTS 719,648 Great Britain Dec.8, 1954

1. AN IMPROVED FUEL COMPOSITION COMPRISING A MAJOR PORTION OF AHYDROCARBON FUEL AND A MINOR PORTION, SURFFICIENT TO REDUCE THEDEPOSIT-FORMING CHARACTERTISTICS OF SAID FUEL, OF A RELATIVELY HIGHMOLECULAR WEIGHT COPOLYMER OBTAINED BY THE COPOLYMERIZATION OF (A)MONOMERS SELECTED FROM THE GROUP CONSISTING OF ALIPHATIC ESTERS OFMETHACRYLIC ACID AND ACRYLIC ACID CONTAINING 8 TO 30 CARBON ATOMS AND(B) MONOMERS SELECTED FROM THE GROUP CONSISTING OF METHACRYLIC ACID ANDACRYLIC ACID IN WHICH THE RATIO OF (A) TO (B) IN WITHIN THE RANGE OF 0.5TO 10, AND IN WHICH ABOUT ABOUT 5 TO 60% OF THE CARBOXYL GROUPS OF (B)ARE PRESENTED IN THE FORM OF MONOCESTERS OF POLYALKYLENE GLYCOLSSELECTED FROM THE GROUP CONSISTING OF POLYETHYLENE GLYCOL HAVING AMOLECULAR WEIGHT UP TO ABOUT 800 AND MONOALKYL ETHERS OF SAIDPOLYETHYLENE GLYCOL.